Instrument for manipulating spinal implant system

ABSTRACT

Instruments are provided herein for reducing the lateral distance between a spinal rod anchored to a spine and a coupling device. The instruments permit a rod to be shifted into a coupling device that is not in alignment with other coupling devices secured to the rod because of rotational deformities causing one or more vertebrae to be shifted with respect to at least one other vertebra.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application Ser.No. 60/889,449, filed Feb. 12, 2007, and entitled “Instrument forManipulating Spinal Implant System,” which is hereby fully incorporatedby reference as if set forth herein.

FIELD OF THE INVENTION

The invention relates to an instrument for manipulating and securing aspinal rod relative to a spine and, more particularly, to an instrumentfor securing a spinal rod to one or more coupling devices fixed to thespine.

BACKGROUND OF THE INVENTION

In a number of surgical procedures, implant devices are utilized topromote the healing and repair of various parts of the human body. Insome cases, implant devices secure bones or bone segments relative toeach other so that the bones themselves may heal, fuse, or berepositioned. For instance, two or more vertebrae of the spinal columnmay be linked together by a plate or an elongated rod member in order toprevent relative movement between the vertebrae. In addition, anelongated rod may be used to correct spinal deformities, includingrotating or de-rotating one or more vertebrae relative to at least oneother vertebra. For instance, in treatments for scoliosis, undesirabletorsion of the spine is corrected by “de-rotating” one or more rotated,out-of-phase vertebrae to place them in proper rotational alignment withthe other vertebrae.

Typically, implanting devices that secure bones or bone segmentsrelative to each other involves securing a plurality of bone screws,hooks, or other fixtures to a plurality of respective bones. Then, eachof the fixtures is secured relative to the others with an additionalapparatus, such as a connecting rod. A pedicle screw and rod system isone such example that is commonly used to connect adjacent vertebraetogether.

In order to align a series of vertebrae, a number of bone screws may besecured to or fastened along the vertebrae. Each screw may be integrallyor rotatably attached to a coupling member, which includes physicalstructures for coupling a bone screw to a connecting rod. Often, thecoupling member includes opposed, upstanding walls to form a yoke withinwhich the connecting rod is retained. Each coupling member may besecured with, and relative to, at least one other coupling member withthe spinal rod. A locking member, such as a locking cap, is locked intothe coupling member to lock the spinal rod relative to the couplingmember.

A number of methods may be used to lock a spinal rod within a couplingmember. Traditional locking caps require at least partial rotation of acap relative to a coupling member in order to loosely secure the cap tothe coupling member. Further rotation of the cap provides additionallocking force that compresses the rod into the coupling member and locksit into place. Many pedicle screws, for instance, utilize a threadedlocking cap that engages threads on the interior or exterior of the yokeso that rotation of the cap relative to the yoke results in linearmovement of the locking cap toward the spinal rod. Threading the capincrementally into the coupling member causes an incremental increase inthe force securing the spinal rod. When the cap is rotated enough times,a clamping force is provided to secure the rod between the yoke and thelocking cap. Other locking devices (such as in U.S. Pat. Nos. 5,084,049to Asher; 6,565,565 to Yuan; and 6,755,829 to Bono) include discreteflanges or slots that may be lowered onto or into a coupling member andthen twisted into place with a partial rotation to at least looselycapture a spinal rod within the coupling member. In such devices, thelocking member will simply fall out of the coupling member unless theflanges or slots are rotated into contact with corresponding structureson the coupling member. Alternatively, a novel, linearly-insertedlocking cap assembly has been provided in U.S. patent application Ser.No. 11/839,843, filed Aug. 16, 2006 (which is incorporated by referenceas if fully described herein), wherein flexible portions of the walls ofthe coupling member or yoke flex outward and inward to capture alinearly-inserted cap in a snap-lock fit. In one device disclosed inthat application, a cap is inserted into the yoke without rotation to afirst snap-lock position within the yoke, at least loosely capturing therod within the yoke. Further insertion may lead to one or moreadditional snap-lock positions. The locking cap may further beconfigured so that rotation of at least a portion of the locking capassembly when received in the yoke to provide additional locking force,pushing a bottom surface of the cap assembly against the spinal rod andlocking the rod into place.

When securing a rod to the spine, the fixation members implanted intothe vertebrae may not be perfectly aligned for receipt of a straightrod. In such cases, the rod may be bent to conform to the fixationmembers, or the vertebrae may be rotated slightly to align the fixationmembers. However, in some applications, a spinal deformity is correctedby shifting and/or rotating the vertebrae to conform to a rod with apreselected shape. For instance, coupling members may be anchored alongthe vertebrae so that each coupling member is in relatively the sameposition with respect to its vertebra as other coupling members are totheir respective vertebra, so that when the coupling members are alignedalong a straight rod, the vertebrae are rotated and forced intoalignment. In such cases, aligning the coupling members anchored to thevertebrae along the rod is often difficult, requiring a significantamount of torque to be applied to the patient's spine in order to rotatethe coupling devices and their respective vertebrae into axialalignment. Maintaining the positioning of the coupling devices, locatinga connecting rod into the aligned coupling devices, and locking the rodwithin the coupling members while the vertebrae are under significanttorsional stress all presents further challenges.

There remains a need for an improved implant manipulation instrumentthat may apply the force required to draw a spinal rod laterally intoalignment with a coupling member anchored to a vertebra. There alsoremains a need for a device that is able to secure and lock a rod intoplace within a coupling member anchored to a vertebra whilecounteracting torque created by undesirable rotation or otherdeformities of the spine.

SUMMARY OF THE INVENTION

The present invention is related to devices and methods to aid inmaneuvering and securing an implantable structure, such as a spinal rod,to a fixation device, such as a pedicle screw or vertebral hook.

An instrument is provided for reducing or eliminating the lateraldistance between a coupling member (or yoke) fixed to a first vertebraand an adjacent spinal rod fixed to at least two other vertebra. Theinstrument comprises a clamp device for clamping the yoke fixed to thevertebra; a persuader arm pivotably connected to the clamp device thatengages a spinal rod and manipulates the rod to locate it in the yokesecured by the clamp; and a drive device to axially insert a locking capinto engagement with the yoke to secure the spinal rod therebetween. Thepersuader arm is configured so that the rod may be positioned into theyoke without disengaging the persuader arm from the rod. The drivedevice may be configured to be inserted axially through the persuaderarm in order to insert the locking cap into the yoke while the rod iscontacting both the yoke and the persuader arm. The drive device ispreferably an assembly including a component that axially advances thelocking cap toward the yoke into one or more axial positions, and acomponent that rotates the cap into one or more rotational positions.

The instrument may include a ratchet mechanism capable of restrictingthe pivoting motion of the persuader arm away from the clamp device, butpermitting pivoting of the persuader arm toward the clamp device,thereby allowing the rod to be pulled toward the yoke secured to theclamp device but preventing the rod from moving away from the yoke dueto forces created by the shape and contortion of the spine.

An axial adjustment lock assembly may also be included in theinstrument. The axial adjustment lock engages and disengages thepersuader arm to control axial movement of the arm. When the axialadjustment lock assembly is disengaged, the persuader arm may be freelyadjusted axially in order easily extend the persuader arm intoengagement with the rod. Once the persuader arm has captured the rod,the axial adjustment lock assembly may be engaged to prevent free axialmovement so that the persuader arm may manipulate the rod without beingmoved axially by torque from the spine. Preferably, the axial adjustmentlock assembly provides for ratcheted retraction of the persuader arm sothat the persuader arm may be incrementally retracted to move the spinalrod toward the coupling member secured to the instrument.

The disclosed instrument may be used, for instance, with a system forsecuring a spinal rod where a locking cap is linearly advanced into oneor more locking positions within a yoke, and then rotated to provide oneor more additional locking positions that further restrict movement of arod received in the yoke.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevation view of a portion of a spine in which onevertebra is rotated relative to the adjacent vertebrae;

FIG. 2 is a view of the instrument without the persuader arm insertedinto the guide portion;

FIG. 3 is a view of the instrument with the persuader arm inserted intothe guide portion;

FIG. 4 is a view of the instrument engaging a yoke laterally displacedfrom a spinal rod;

FIG. 5 shows the instrument clamping to a yoke laterally displaced froma spinal rod;

FIG. 6 shows the persuader arm being inserted into the instrument whenclamped to a yoke;

FIG. 7 shows the persuader arm of the instrument being extended tocapture a spinal rod adjacent to the yoke to which it is clamped;

FIG. 8 is a view of the persuader arm of the instrument capturing aspinal rod;

FIG. 9 shows the instrument having shifted a spinal rod to a positionabove the yoke to which the instrument is attached;

FIG. 10 shows the persuader arm traveling linearly to position a spinalrod into a yoke;

FIG. 11 is a cross-sectional view of the persuader arm positioning aspinal rod above a yoke;

FIG. 12 is a side elevation view of a drive device and locking cap beinginserted into the persuader arm of the instrument;

FIG. 13 is a side elevation view of the drive device with a locking capreleasably secured thereto at the distal end;

FIG. 14 is a cross-sectional view of the instrument positioning thespinal rod in the yoke, with the drive device inserted coaxially intothe persuader arm;

FIG. 15 shows the instrument with its clamp device in an open position,engaging the yoke;

FIG. 16 shows the instrument clamping the yoke;

FIG. 17 is a side cross-sectional view of the instrument beforeclamping;

FIG. 18 is a side cross-sectional view of the instrument clamping theyoke;

FIG. 19 is a rear cross-sectional view of the clamping device before theactuator activates the clamping mechanism;

FIG. 20 is a rear cross-sectional view of the clamping after theclamping mechanism is engaged;

FIG. 21 is an exploded view of the instrument, without the drive devicefor inserting the locking cap;

FIG. 22 is an exploded view of the central operating assembly;

FIG. 23 is a perspective view of the ratchet mechanism;

FIG. 24 is a rear cross-sectional view of the instrument showing part ofthe clamp device actuating mechanism;

FIG. 25 is a cross-sectional view of the central operating assembly;

FIG. 26 shows the axial lock mechanism for the persuader arm in adisengaged position;

FIG. 27 shows the axial lock mechanism for the persuader arm in andisengaged position;

FIG. 28 is a side elevation view of the engagement portion of thepersuader arm;

FIG. 29 is a cross-sectional view of the engagement portion of thepersuader arm;

FIG. 30 is a detailed view of the distal end of the drive device and alocking cap to be secured thereto;

FIG. 31 is an exploded view of the drive device, showing the distal endsof the inner and outer shaft members; and

FIG. 32 is an exploded view of the drive device, showing the proximalends of the inner and outer shaft members.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In one form, the instrument disclosed herein has a central housingcontaining a ratchet mechanism or assembly, with a ratchet handle andclamp device extending from the housing. A persuader arm is provided andconfigured for pivotal movement by operation of the ratchet handle. Thepersuader arm may be releasably secured to, and preferably insertedcoaxially into, the ratchet handle. The clamp device of the instrumentis configured to clamp to a coupling member, for instance the yoke of abone screw, when the coupling member is anchored to a bone. Thepersuader arm is configured to extend from the instrument to capture aspinal rod, and to maneuver the spinal rod toward the clamp device inorder to position the rod in the coupling member or yoke clamped withinthe clamp device.

Once a surgeon has secured the instrument to the yoke, the clamp deviceor member holds the yoke with sufficient clamping force so that theinstrument is secured to the spine and need not be held in place by thesurgeon.

During operation, the persuader arm captures a spinal rod that ismounted to the spine in a position laterally spaced from the yoke. Theratchet handle and persuader arm are pivoted with respect to the clampdevice in order to maneuver the rod toward the clamp device. The ratchetassembly allows this pivoting to be accomplished incrementally,advantageously permitting additional surgical steps to be taken atintervals during manipulation of the rod. The persuader arm may also beretracted incrementally toward the instrument, preferably by turning athreaded portion of the persuader arm within a guide portion.

The persuader arm is retracted and pivoted, drawing the rod toward theinstrument, until the rod is positioned axially above an opening in theyoke for receiving the spinal rod. The persuader arm is thenincrementally advanced toward the yoke until the rod is positioned inthe yoke. Preferably without disengaging the persuader arm from the rod,a drive device may be used to axially insert a locking cap intoengagement with the yoke in order to lock the rod in place.

Advantageously, the steps of laterally moving the rod and the yoke,positioning the rod within the yoke, and locking the rod to the yoke mayall be accomplished using a single instrument and without disengagingthe rod between the positioning and locking steps.

The instrument 100 described herein is especially useful for de-rotatinga spinal column experiencing rotational deformity, as in FIG. 1. Arotated intermediate vertebra 2 is rotated or shifted with respect totwo adjacent vertebrae 1 and 3. Vertebrae 1 and 3 are connected by arigid spinal rod 4 captured by fixation members in the form of bonescrew assemblies having yokes 5 and 6 mounted to and extending dorsallyfrom vertebrae 1 and 3, respectively. The spinal rod 4 connecting yokes5 and 6 is depicted as straight, having an axis parallel to the axis ofthe partial spinal column, and connecting two yokes 5 and 6 that areaxially aligned along the spine to permit connection by the spinal rod4. However, the yokes 5 and 6 need not be perfectly axially aligned, andthe spinal rod 4 may experience some bending in order to be disposed inyokes 5 and 6. Yokes 5 and 6 may be any type of top loading bone screwsdesigned to receive a spinal rod. The spinal rod 4 is held in place inthe yokes 5 and 6 by locking caps 8.

An intermediate yoke 7, located axially between screw assemblies 5 and 6along the axis of the spinal column and mounted to the intermediatevertebra 2, is out of phase with respect to the two adjacent yokes.Torsion of the intermediate vertebra 2 as a result of one or more spinaldeformities has resulted in a lack of axial alignment between theintermediate vertebra 2 and adjacent vertebrae 1 and 3. The intermediateyoke 7 therefore is out of alignment with yokes 5 and 6, despite beinganchored in the same relative position along its associated vertebra asadjacent yokes 5 and 6 to their respective vertebrae. The positioning ofthe intermediate yoke 7 is such that aligning the yoke 7 axially withadjacent yokes 5 and 6 will consequently shift the intermediate vertebra2 roughly into axial and rotational alignment with the adjacentvertebrae 1 and 3.

With continued reference to FIG. 1, connecting the intermediate yoke 7to the spinal rod 4 requires significant shifting of the rod 4, sincethe entire lateral distance between the rod 4 and the intermediate yoke7 must be eliminated by overcoming the torsion between vertebrae 1, 2,and 3. The rod 4 and intermediate yoke 7, both of which are mounted tothe spine, may be captured by an instrument 100 disclosed herein andused as anchor points by the instrument 100, which provides a lever formanipulating and shifting the yoke 7 and rod 4 together to eliminate anylateral distance therebetween and positioning the rod within the yoke.

A perspective view of one embodiment of the instrument 100 is shown inFIG. 2. The instrument 100 contains a central housing 91 containing acentral operating assembly. Extending from the central housing 91 are aratchet handle 10 that pivots with respect to the housing, a clampdevice 20, and a pivotable clamping actuator lever 21. The ratchethandle 10 and actuator lever 21 extend generally radially from thehousing and pivot about an operating axis 104. In the illustratedembodiment, the clamp device 20 is integrally formed with the centralhousing 91. A ratchet dial 30 for operatively engaging a ratchetassembly 133, which when turned to a locked position inhibits pivotingbetween the ratchet handle 10 and the clamp device 20 in one direction,is located on the side of the housing 91 along the operating axis 104.

The clamp device 20 is a hollow elongated portion comprising at one endtwo parallel flexible legs 25 a and 25 b separated by a slit 23 (asshown in FIG. 3). Each flexible leg contains outwardly-extending arms 22a and 22 b configured to receive and hold the yoke. The two parallelflexible legs 25 a and 25 b are shown formed integrally as part of aone-piece clamp device, but it will be understood that the clamp devicemay also comprise an assembly of separate structures that are movablewith respect to each other.

Located on the central housing opposite the ratchet dial 30 is a button50, as shown in FIG. 3, which may be pressed inward. The button controlsan axial adjustment lock subassembly 59 that locks and unlocks an axialthroughbore in the ratchet handle 10 (as shown in more detail in FIGS.25-27). Pushing in the button 50 allows a persuader arm 60 to beslidably inserted through the ratchet handle 10, which serves as a guidedevice for the persuader arm 60. Alternatively, the guide device may beseparate from the ratchet handle. The persuader arm 60 contains athreaded portion 63 along a shaft 61, and a distal engagement portion 64configured to capture the spinal rod. Pivoting of the ratchet handleguide device 10 moves the persuader arm engagement portion 64 toward andaway from the clamp device 20.

The instrument 100 is used to shift the laterally-positioned yoke 7 intoalignment with the spinal rod 4, as shown in FIGS. 4-10. The instrument100 is first secured to the implanted yoke 7 by engaging it with thearms 22 a and 22 b of the clamp device 20, as shown in FIG. 4. Once theclamp device is in place, the clamp actuator lever 21 is pivoted towardthe ratchet handle 10 in order to clamp the yoke 7 in place. As will bedescribed in detail later, movement of the actuator lever 21 causes thelegs 25 a and 25 b of the clamp to flex inward, locking the yoke 7 inplace between the clamp arms 22 a and 22 b.

Once the instrument 100 is clamped to the yoke 7, the persuader arm 60is positioned within a guide portion, which in this case also forms theratchet handle 10. The ratchet dial 30 is rotated to an unlockedposition in order to allow the ratchet handle 10 to pivot while thepersuader arm 60 is inserted therein. The persuader arm 60 is insertedaxially through a throughbore 11 in the ratchet handle 10. The axialadjustment lock subassembly 59 is disengaged so that the persuader arm60 may freely slide into the throughbore 11.

The persuader arm 60 is slidably extended toward the laterally spacedrod 4 as in FIG. 7. The head or engagement portion 64 of the persuaderarm contains a hooked portion 147 in order to engage the spinal rod 4 ata side diametrically opposite the ratchet handle 10. The ratchet handle10 is then pivoted in order to guide the persuader arm 60 so that theengaged portion 64 captures the rod 4, as in FIG. 8. An axial adjustmentlock subassembly 59 within the central operating assembly 90 at thispoint may be permitted to engage the threaded portion 63 on the exteriorof the persuader arm 60 to limit extension thereof (shown in FIGS.25-27).

The ratchet dial 30 can be rotated to a locked position to preventangular movement of the ratchet handle 10 away from a vertical position(which would allow the rod 4 to slide out of engagement with theengagement portion hooks 147). When in the locked position, the ratchetassembly 133 (shown in FIGS. 22-23) permits pivoting movement of theratchet handle 10 in an upward arc only, so that the handle may be movedonly toward a vertical position, thereby moving the persuader armengagement portion 64 closer to the clamp device 20.

In most cases, axial movement of the persuader arm 60 is also desirableor necessary in order to raise the rod 4 above the level of the yoke 7during pivoting. In order to position the rod 4 above the yoke 7, thepersuader arm should be axially retracted through the ratchet handle 10during pivoting. A drive mechanism is provided for incrementally movingthe persuader arm 60 in an axial direction, comprising threads 63 on theexterior of the persuader arm 60 that are engageable with threads of theaxial adjustment lock subassembly 59, described later in reference toFIGS. 25-27.

The persuader arm 60 is retracted and pivoted until the rod 4 iscaptured in the engagement portion 64 is located above the yoke 7, as inFIG. 9. Specifically, positioning of the rod is accomplished by rotatingthe persuader arm 60 as described above, and by ratcheting the persuaderarm into a vertical position by squeezing the handle 10 and actuatorlever 21 together, drawing the handle 10 upright into a verticalposition. Since the handle 10 is locked in place by the ratchet assembly133, the process of rotating the handle 10 into vertical alignment maybe achieved incrementally, allowing additional surgical steps to takeplace at various stages of drawing the rod 4 toward the yoke 7. In fact,the surgeon may alternate between retracting and rotating the persuaderarm 60 in order to carefully pull the spinal rod 4 toward the yoke 7 andde-rotate the spine. A cross section of the persuader arm 60 engaged tothe spinal rod 4 is shown in FIG. 11.

The spinal rod 4 is then shifted into the yoke 7, as shown by FIG. 10.Once the rod is drawn to a point above the yoke by axial retraction andpivoting of the persuader arm 60, the persuader arm 60 may be linearlyadvanced toward the yoke 7 by rotation in the opposite direction used toretract the persuader arm. The persuader arm engagement portion 64 ishollow and configured to be lowered over the yoke 7 to load the spinalrod 4 therein. The persuader arm engagement portion 64 engages thespinal rod 4 at axially spaced positions farther apart than the diameterof the yoke, so that no portion of the persuader arm engagement portion64 is trapped between the rod 4 and yoke 7 as the rod is lowered intothe yoke.

After the rod 4 has been positioned within the yoke 7, a drive device170 may be inserted into an axial throughbore in the persuader arm 60 inorder to drive the locking cap 8 into locking engagement with the yokesituated within the persuader arm engagement portion 64, as shown inFIG. 12. The drive device comprises an outer shaft member 171 in whichan inner shaft member 172 is coaxially disposed, as seen in FIG. 14. Theinner shaft member is rotatable within the outer shaft member 171, asseen in FIG. 14. The locking cap 8 is releasably secured to the distalend of the drive device 170. A bearing member 190 attached to the distalend of the drive device 170 holds the locking cap 8 into place.

The drive device 170 has a threaded portion 183, an outside diametersuch that it can be inserted coaxially into the persuader arm 60, andinto engagement with a threaded interior portion 184 of the persuaderarm, as seen in FIG. 14. The drive device 170 is inserted axially intothe persuader arm 60 until threads 183 on the drive device 170 engagethreads 184 on the interior of the persuader arm. At that point, theouter shaft 171 of the drive device must be rotated in order to provideadvancement of the drive device toward the yoke. A drive head portion180 is provided at the proximal end and may be engaged with a wrench toadvance the drive device downward toward the yoke 7.

Axially driving the drive device 170 and a locking cap 8 releasablysecured thereto into engagement with the yoke 7 inserts the locking capinto the yoke 7, as seen in FIG. 14. In one form, linearly advancing thecap into the yoke at least partially locks the cap into the yoke. Thelocking cap and yoke may optionally be configured to enter into aplurality of locking positions as the locking cap 8 is axially insertedinto the yoke, and the cap may also be configured to enter one or morelocking positions as it is rotated relative to the yoke 7 after axialinsertion. Rotation of the inner shaft member 172 causes rotation of thelocking cap 8, and the locking cap 8 and yoke 7 may therefore also beconfigured so that rotation of the locking cap 8 within the yoke 7achieves one or more locking positions.

Clamping of the clamp device 20 to a coupling member having an anchormember mounted to the spine, such as the illustrated yoke 7, isaccomplished by moving the clamping actuator lever 21 to clamp andunclamp the clamp device 20, as illustrated in FIGS. 15-20. When theactuator lever 21 is rotated upward, toward the ratchet handle 10, theflexible members 25 a and 25 b of the clamp device are drawn together bythe movement of a plunger (27 in FIGS. 17-20) that is operated by theactuator lever 21. As the flexible members 25 a and 25 b are drawntogether, a clamping force is provided sufficient to secure the yoke 7between outwardly extending arms 22 a and 22 b connected to the flexiblemembers.

The side cross-sectional views in FIGS. 17 and 18, further illustratesthe operation of the plunger 27 within the clamp device. As the clampactuator lever 21 is moved toward the ratchet handle 10, a catch 71extending radially from the axis of rotation of the lever 21 is moveddown (clockwise in the view shown), engaging a catch 29 on a stop member28, driving the stop member and attached plunger 27 downward through thehollow portion of the clamp device. Two laterally extending posts 24traverse the hollow portion. As the plunger 27 moves axially through thehollow portion of the clamp device 20 and away from the central housing,a recess 110 at the bottom of the plunger engages both posts 24 andforces them together, drawing the flexible portions of the clamp devicetogether and resulting in a clamping force sufficient to secure the yoke7. Seen from a rear cross-section, as in FIGS. 19 and 20, as the plunger27 is forced downward through an axial hollow portion 145 in the clampdevice 20, inwardly-sloped surfaces 111 on the plunger 27 direct the twospaced-apart posts 24 traversing the hollow portion 145 toward a concaverecess 110 in the plunger 27, as illustrated in FIGS. 19 and 20. Therecess 110 is sized and configured to receive both posts 24 when spacedclose together, but is not wide enough to receive the posts when spreadapart in their normal spatial relationship. Therefore, when the plunger27 is forced downward through the hollow clamp device, the plunger drawsthe posts 24 together, which in turn draws together the flexible legs 25a and 25 b of the clamp, reducing or eliminating the width of the slit23 formed between the flexible portions and resulting in a clampingaction between the arms 22 a and 22 b. A full rear cross-section may beseen in FIG. 24.

Turning now to the details of the central operating assembly of theinstrument 100 in FIG. 21, an exploded view of the main body andpersuader arm of the instrument 100 display components of the clampdevice 20, persuader arm 60, and central operating assembly 90(including the ratchet assembly 133 and axial adjustment locksubassembly 59). As described previously, clamping actuator lever 21,ratchet handle 10, and clamp device 20, which is formed integrally witha central housing 91, are configured to be pivotally connected to eachother. Assembly of the clamping actuator lever 21, ratchet handle 10,and clamp device 20 involves aligning a large aperture in each memberalong a common rotational axis and inserting a piston 51 through each ofthe aligned apertures to pivotally secure the members. The piston 51also forms a portion of the central operating assembly, which actuallycomprises two separate subassemblies: the ratchet assembly 133 forfixing the angular position of the pivoting handle 10 and the axialadjustment lock subassembly 59 for engaging and disengaging theadjustable persuader arm 60, allowing the adjustable persuader arm 60 toslide into place within the hollow pivotable handle 10 and then becomelocked therein against sliding axial movement.

The ratchet assembly 133, which is described further with respect toFIGS. 22-23 comprises a ratchet dial 30 secured by a central bolt 31 andtwo smaller, radially spaced guide bolts 32, the ends of which arehoused in retaining members 33 that are partially disposed in arcuateslots 93 of the housing 91. The central bolt 31 is partially threaded,so that the unthreaded portion nearest the head allows for smoothrotation of the ratchet dial 30 while the threaded portion of thecentral bolt 31 secures the ratchet dial to the assembly. The retainingmembers 33 help to hold the ratchet dial 30 to the housing 91 and limitrotation of the ratchet dial 30 to a predetermined angular value basedon the size and configuration of the guide slots 92. The ratchetassembly 133 further comprises a cylindrical ratchet drum 34, inside ofwhich is disposed a cylindrical radially expanding spring 37. In thiscase, the ratchet drum 34 is formed integrally with the piston 51.Camming ratchet teeth 38 are disposed radially outside of the radiallyexpanding spring 37 and radially inside of the cylindrical ratchet drum34, with the ends of the ratchet teeth extending radially outwardthrough circumferentially opposed slots 39 in the ratchet drum 34.

The axial adjustment lock subassembly 59 comprises the piston 51 havinga solid end forming an exterior depressible button 50 and also having aninterior channel 53 situated transverse to the long axis of the piston.At least a portion of the interior of the transverse channel 53 isthreaded. The axial adjustment lock subassembly 59 further comprisesleaf springs 54 and 55 spaced by a washer 56 that serve to bias thepiston 51 outward when it is not manually depressed by the surgeon.

With continued reference to FIG. 21, an actuating plunger 27 is providedthat slides into the hollow portion of the clamp device 20 andtranslates linearly through the clamp in order to clamp and unclamp theflexible legs 25 a and 25 b of the clamp device 20, as described above.The actuating plunger 27 is moved linearly by movement of the clampingactuator lever 21, which contains a catch 71 that pushes against acorresponding catch 29 on a stop member 28 that is secured to theplunger 27 by a bolt 58. The plunger 27 has an arcuate recess 110 at itsfree end, the recess 110 being designed to engage and force togetherlaterally extending posts 24 traversing the hollow portion of the clampdevice 20, as demonstrated in FIGS. 19-20.

In one form, the persuader arm 60 is provided as a separate, elongatecylindrical member that may be disposed concentrically within theratchet handle 10, which forms a guide portion or locking sleeve thatallows the persuader arm 60 to slide axially and then be locked in placethrough use of the axial adjustment lock subassembly 59. The persuaderarm distal engagement portion 64 contains a detent mechanism 65 forsnap-locking to the persuader arm shaft 61 and being rotatable withrespect thereto.

Further details of the central operating assembly 90, including theratchet assembly 133 and axial adjustment lock subassembly 59, are shownin FIG. 22. Advantageously, the two subassemblies share certaincomponents, which reduces the size and general profile of the instrument100; facilitates assembly, disassembly, and cleaning; and economizesmanufacture. As illustrated, the housing 91 for the assembly is formedintegrally with the clamp device 20, but it will be readily understoodthat the housing may be formed separate from the clamp device. Thehousing 91 is located along the central operating axis 104 and isbounded on axial ends by collars 130 and 131, each having an aperture.The ratchet collar 130 forms part of the ratchet assembly 133. Theopposed open collar 131 is wide enough to receive components of the twosubassemblies.

The ratchet assembly 133 comprises a cylindrical ratchet drum 34. In theillustrated embodiment, the ratchet drum 34 is formed integrally withthe piston member 51. Located circumferentially and coaxially inside theratchet drum 34 lies a ratchet mounting member 57, to which a ratchetdial 30 is mounted when assembled.

Two sets of ratchet teeth 38 are provided in the ratchet assembly 133.The teeth are inserted into circumferentially-spaced slots 39 in theratchet drum from the interior of the drum. Base portions 38 a of theratchet teeth form tabs that retain the teeth 38 in the slots 39. Thebase portions also extend slightly beyond the axial edge of the ratchetdrum when the teeth 38 are disposed in the slots 39.

A radially expanding spring 37 is inserted concentrically and coaxiallywithin the ratchet drum 34 and ratchet teeth 38, so that the exterior ofthe spring 37 contacts the bases of the ratchet teeth 38, biasing theteeth radially outward through the slots 39 in the ratchet drum. Thespring 37 has a first diameter when less than a predetermined force isapplied to its exterior, and is configured to contract radially to asecond diameter when a radial force equal to or greater than thepredetermined force is applied. In a resting state, the teeth protrudefully out of the circumferentially-spaced slots 39. However, when thespring 37 is compressed radially, the ratchet teeth 38 are allowed toretract into the circumferentially-spaced slots 39.

The ratchet drum 34, having been assembled with the ratchet teeth 38 andthe radially expanding spring 37 so that the teeth and spring are heldconcentrically and coaxially within the drum 34, is inserted axiallythrough the central operating housing 91 toward the ratchet collar 130formed on the housing. The ratchet dial 30 approaches the ratchet collar130 from an opposite direction, and is secured to the ratchet mountingmember 57 using a mounting bolt 31. The mounting bolt 31 is threaded atone end so that it may be fixed within a threaded opening in themounting member 57, but is unthreaded along a length of its shaft nearthe head in order to allow smooth rotation of the ratchet dial 30. Themounting bolt 31 extends through the aperture of the ratchet collar 130in order to secure the ratchet dial 30 to the mounting member 37. Theaperture in the ratchet collar 130 is of a sufficiently small diameterso that neither the piston 51 nor the ratchet dial 30 may pass throughit, effectively confining the ratchet assembly 133 to the centralhousing 91.

When the ratchet assembly 133 is disposed in the central housing 91, theratchet teeth 38 are aligned radially with housing teeth 92 locatedwithin the aperture of the ratchet collar 130. The ratchet teeth 38 maybe extended and retracted radially to engage and disengage the housingteeth 92 by expansion and compression of the radially expanding spring37 of the subassembly.

Two small guide bolts 32 are also disposed in the ratchet dial 30,radially spaced from the center of the dial and the mounting bolt 31disposed therein. The guide bolts 32 pass through the ratchet dial 30and attach to retaining members 33 that are configured to glide inarcuate slots 93 on the outward face of the housing collar 130. Thepaths of the arcuate slots 93 are dimensioned to provide limitedrotation of the ratchet dial 30 from a discrete locked position to anunlocked position.

A recess 145 in the interior of the ratchet dial 30 is configured toradially retract and extend the ratchet teeth 38 when turned, as shownin FIG. 23. The perimeter of the recess 145 is non-circular when viewedalong the rotation axis 104, so that the perimeter is narrower in afirst radial direction than a second radial direction. In order to setthe ratchet assembly 133 in an unlocked position, the ratchet dial 30 isrotated so that the narrow diameter of the recess is aligned with thetabs on the ratchet teeth 38 a, applying a radial inward force thatpushes the ratchet teeth 38 inward and compresses the radial spring 37.When the ratchet dial 30 is rotated so that a wide diameter of thecamming recess 145 is aligned with the tabs 38 a on the ratchet teeth 38(the orientation shown in FIG. 23), the radial spring 37 is allowed toexpand, pushing ratchet teeth 38 radially outward so that the tips ofthe teeth extend through openings in the ratchet drum 34 and engagecomplementary teeth on the ratchet collar 130 of the housing.

In discussing the ratchet assembly 133, reference to “clockwise” and“counterclockwise” will be made relative to the perspective shown inFIG. 23, which shows the side of the instrument 100 containing theratchet dial 30. The ratchet assembly 133 operates by advancing ratchetteeth 38 from the assembly into engagement with complementary teeth 92on the housing. When ratchet teeth 38 and housing teeth 92 aredisengaged, free rotation of the ratchet drum 34 is permitted within thehousing. However, the ratchet teeth 38 and housing teeth 92 areconfigured to permit rotation in only one rotational direction uponengagement, providing a ratchet lock between the housing and ratchetassembly 133. This ratchet lock is accomplished by providing one-waysloped tips on the ratchet teeth 38 that are complementary to one-waysloped tips on the housing teeth 92, so that the sloped tips slide pasteach other when the ratchet handle 10 is rotated counterclockwise withrespect to the housing. However, the sloped tips of the complementaryteeth resist rotation in the opposite direction, since parallel surfaceson the two sets of teeth abut upon attempted rotation in that direction.

The axial adjustment lock subassembly 59 will now be described withreference to FIG. 22. The axial adjustment lock subassembly 59 comprisesleaf springs 54 and 55 separated by a washer 56, and a piston 51. Thesprings 54 and 55 shift the piston member along the operating axis 104in order to lock the position of the extendable persuader arm 60 intoplace in the transverse channel 53 of the piston. The piston 51 isdisposed within the central housing 91 of the instrument 100 along theoperating axis 104. The base 120 of the pivotable ratchet handle 10 isalso received in the housing 91, with the piston 51 being disposedthrough the transverse passage 115 through the handle base 120.Therefore, securing the piston 51 in the housing 91 simultaneouslypivotably secures the handle 10 to the housing. The clamping actuatorlever 21 is similarly held in the housing by the piston 51.

The open collar 131 opposite the ratchet collar 130 contains an aperturehaving a diameter large enough to slidably receive the piston 51. Thecentral portion of the housing 91 is open from the top and side toreceive the base 120 of the pivotable handle 10. As described above, thehandle member 10 comprises a sleeve or axial guide. The base 120 of thehandle member contains an open transverse channel 115 transverse to thecylindrical axis of the handle. The transverse channel 115 is alignedalong the operating axis 104 within the central housing 91 duringassembly, and slidably receives the piston member 51.

When the piston member 51 is received in the transverse channel 115 ofthe ratchet handle 10, the open channel 53 through the piston is alignedwith the axial channel though the ratchet handle 10 so that a persuaderarm may pass through both the handle and piston. When assembled, thepersuader arm runs through the axial channel forming the hollow portionof the ratchet handle 10, through the opening 53 in the piston member,and exits an axial opening 116 at the bottom of the handle base 120. Inorder to align the opening 53 in the piston with the axial channel andaxial opening 116 of the ratchet handle 10, an alignment recess 113 isformed along the exterior surface of the piston 51, with a correspondingalignment recess 117 on the interior of the transverse channel 115 ofthe handle member. When alignment recesses 113 and 117 face each other,the transverse passage 53 in the piston is aligned with the axialchannel 11 of the ratchet handle 10. An alignment pin 114 is disposedbetween alignment recesses 113 and 117 in order to prevent rotation ofthe piston member 51 relative to the opening 116 in the handle base 120.The alignment pin 114 should be configured to prevent rotationalmovement, but to allow axial movement of the piston within thetransverse channel 115 of the handle base 120. Alternatively, the pistonmay be rotationally fixed within the transverse channel of the handleportion by a ridge or groove formed on the surface of the piston that iscomplementary to a ridge or groove on the interior of the transversechannel of the handle, eliminating the need for the alignment pin 114.

The transverse throughbore 53 in the piston 51 is wider than the axialopening 116 of the handle 10 so that axial movement of the piston ispermitted even when the persuader arm is disposed through thethroughbore 53 of the piston and the axial handle base opening 116. Oneside of the transverse throughbore 53 through the piston containsthreads configured to engage a threaded portion of the persuader arm.The piston member 51 is biased outward by leaf springs 54 and 55 so thatthe threads on the interior of the throughbore 53 in the piston 51engage the persuader arm in a resting position. The leaf springs areseparated by a washer 55 against which each leaf spring may compress andexpand. The surgeon operating the instrument 100 may press in the end ofthe piston member 51, which forms a button slightly protruding from thehousing 91, providing an axial force that pushes the piston memberagainst leaf springs 54 and 55, causing the piston member 51 to shifttoward the ratchet collar 130 and disengage the extendable persuaderarm.

Referring now to FIG. 25, a cross-sectional view of the centraloperating assembly 90 is shown. The ratchet dial 30 is shown fixed tothe mounting member 57 radially inward from a ratchet drum 34, with theratchet drum 34 and dial 30 disposed on opposite sides of the ratchetcollar 130 of the housing 91. The ratchet drum 34 is connected to thecylindrical piston 51, which is larger in diameter than the drum 34,forming a drum collar 112 on one side of the ratchet drum. Since thedial 30 and drum collar 112 are too large in diameter to pass throughthe housing collar 130, the ratchet assembly 133 is held in place withinthe housing along the rotational axis 104. Engagement and disengagementof the ratchet teeth 38 and housing teeth 92 is controlled byinteraction between the cylindrical, radially expanding spring 37 andthe recessed surface 145 on the interior face of the ratchet dial 30.The radially expanding spring 37 is disposed concentrically andcoaxially within the ratchet drum 34 and biases the ratchet teeth 38radially outward through openings in the ratchet drum 34. Tabs 38 aextending axially from the ratchet teeth 38 contact the recessedinterior surface 145 of the ratchet dial.

Turning now to the axial adjustment lock subassembly 59, shown incross-section in FIG. 25, the piston 51 is aligned so that itstransverse channel 53 is aligned with the ratchet handle throughbore 11.Leaf springs 54 and 55 bias the piston 51 axially outward through theopen collar 131. The transverse piston throughbore 53 contains threadson one side of its interior.

The persuader arm 60 is inserted into the ratchet handle 10 and engagedand disengaged by the axial adjustment lock subassembly 59 to permit orrestrict axial movement. The axial adjustment lock subassembly 59 isdisengaged, as shown in FIG. 26, by manually depressing the externalbutton 50 formed by the piston, shifting the entire piston 51 axiallyand compressing the leaf springs 54 and 55. When shifted, the persuaderarm 60 may be slidably disposed in the axial channel 11 of the handle 10and freely extended and retracted axially to a length required to engagea spinal rod, since the threads 140 in the transverse opening 53 of thepiston are withdrawn from the path of the persuader arm, and do notengage a complementary threaded portion 63 located on the exterior ofthe persuader arm.

As shown in FIG. 27, when the external button 50 is no longer manuallydepressed, the leaf springs 54 and 55 located at the axially oppositeend of the piston 51 shift the entire piston back outward, causingthreads 140 on the interior of the transverse opening 53 through thepiston 51 to engage the threaded portion 63 of the persuader arm 60passing through the transverse opening 53, forming a drive mechanism.When the threads 140 on the interior surface of the piston throughboreengage the threads 63 on the persuader arm 60, the persuader arm 60 isprevented from sliding axially through the axial guide channel 11 of theratchet handle 10. In this locked position, the persuader arm 60 may beadjusted axially only by rotating it with respect to the interiorthreads 140 of the piston 51. The persuader arm may therefore beincrementally retracted, pulling a spinal rod toward the instrument 100against torsional forces from spinal deformities and the like, withoutworry that the persuader arm 60 will suddenly be extended. When thepersuader arm 60 has been rotated to retract the arm a desired amountwith respect to the ratchet handle 10, the surgeon may leave the rod inplace without worry that the persuader arm will be pulled out of theaxial handle channel 11.

By engaging and disengaging the axial adjustment lock subassembly 59,the persuader arm may be easily slidably extended to the length requiredto engage the laterally-displaced spinal rod, but also has the strengthand ratcheting ability to incrementally draw the spinal rod linearlytoward the instrument 100 in order to de-rotate the spine.

Turning now to details of the persuader arm engagement portion 64, asshown in FIGS. 28-29, axially spaced hook members 147 are configured toengage and capture the spinal rod. A hollow portion 148 is of sufficientsize to receive the yoke into which the spinal rod will be loaded. Thehooks 147 are spaced so that they will engage the spinal rod at axiallyspaced locations. The distance between the hooks 147 is greater than thediameter of the yoke, so that the hooks will not interfere with theloading of the rod into the yoke.

The persuader arm engagement portion 64 snaps into the shaft portion 61and is held in place by detents 65 disposed in corresponding recesses onthe interior surface of the persuader arm shaft portion 61, as shown incross-section by FIG. 29. The engagement portion 64 is rotatable withrespect to the rest of the persuader arm 60 so that the engagementportion 64 may maintain engagement with the rod as the persuader armshaft 61 is rotated to produce linear travel, as described above.

Turning now to details of the drive device 170, the inner shaft member172 is disposed concentrically within the outer shaft member 171, whichin turn may be inserted concentrically within the persuader arm 60, asshown in FIGS. 12-14. Radially outward extending bosses or flanges 193on the bearing member 190 are sized to be received within facing axialslots 150 extending the length of the persuader arm passage. The flanges193 permit the bearing member 190 to slide within the passage, butsubstantially hinder the rotation of the bearing member 190 as the outershaft member 171 is rotated for linear travel through the interior ofthe persuader arm 60. Once the locking cap 8 has been at least partiallyinserted into the yoke, the flanges are free of the axial slots 150 sothat the inner shaft member 172 is now able to rotate the locking caprelative to the yoke for further locking.

An exploded view of the drive device 170 is shown in FIG. 31. Extendingthrough the outer shaft member 171, there extends an inner shaft member172 having a distal tip 188 with a lobed profile arranged and configuredto mate with a lobed recess on the top surface of a locking cap.Assembling the drive assembly 170 involves axially inserting the innershaft member 172 into the passage 186 of the hollow outer shaft member171, and then securing the bearing member 190 to the distal end of theouter shaft member 171 such that the tip 188 of the inner shaft member172 may protrude through an aperture 189 in the bearing member 190 toengage the locking cap.

The bearing member 190 preferably comprises a disk-shaped base member192 with a pair of facing, arcuate upstanding side walls 191 that extendaxially upward from an outer edge of the base member 192. The basemember 192 has a central opening 189 sized to permit the inner shaftmember, and in particular the profiled tip 188, to extend therethrough.The bearing member 190 has an outer diameter permitting receipt withinand passage through the persuader arm 60.

The bearing member 190 is preferably snap-fit onto the distal end of theouter shaft member 171. In one form, the outer shaft member 171 definesan annular ring 187 at its distal end that projects radially outward,and the bearing member 190 includes radial side walls 191 configured tosnap onto the lip 187, such as by having an inwardly facing undercutgroove complementary to the lip 187 on the outer shaft member 187. Inorder to receive the snap ring 187, the bearing member side walls 191preferably resiliently flex outwardly and then snap back into theiroriginal configuration after the lip 187 has been received within theside walls 191.

The bearing member 190 is configured to hold the locking cap 8 in aninterference or friction fit. In one form, the bearing member 190preferably includes arcuate, lock fingers 195 that extend axiallydownward from opposite sides of the base member 192. Preferably, thelock fingers 195 are inclined or tapered radially inward towards thecentral opening 189 in order to receive and releasably secure the cap.In this manner, the drive device 170, and in particular the bearingmember 190, is configured to retain the locking cap 8 thereon whilebeing inserted into the passage through the persuader arm for insertioninto the yoke member 7, but the drive device 170 may be easily removedfrom the cap assembly 8 after it has been locked into the yoke 7 bysimply rotating the outer shaft member 171 in a reverse direction toretract the entire drive device 170. The press or friction fit of thecap assembly 8 to the bearing member 190 will be separated upon thereverse translation of the drive device 170 within the interior of thepersuader arm. To this end, the bearing member 190 should be moretightly bound to the outer shaft member 171 than to the locking cap 8.

In order to advance and rotate the locking cap 8, the proximal end ofboth of outer shaft member 171 and inner shaft member 172 are configuredto engage a rotating instrument 100, such as a wrench, for rotating itsrespective shaft. In this manner, when the inner shaft member 172 isinserted within the outer shaft member 171 to form the drive device 170,engaging and rotating a first portion of the drive device will linearlyadvance the locking cap secured to the distal end of the drive device,and rotation of a second portion of the drive device will cause rotationof the locking cap. FIG. 32 shows an exploded view of the proximal endof the drive device 170. The proximal end of the inner shaft member 172preferably defines a profiled end 185, such as the hexagonal recessillustrated, that permits receipt of a rotating instrument 100 thereon.Likewise, the proximal end of the outer shaft member 171 preferablydefines an exterior profiled end 180, such as the generally square headportion illustrated, that permits receipt of a different rotatinginstrument 100 thereon. In the embodiment shown in FIG. 32, the innershaft member 172 is assembled into the passage 186 of the outer shaftmember 171 so that the profiled end 185 of the inner shaft member isnested concentrically within the profiled head 180 of the drive device.In this manner, a first tool may be used to rotate the profiled head 180of the drive device in order to drive a locking cap axially into a yoketo achieve one or more locked positions, and a second tool may be thenused to engage and rotate the hexagonal recess 185 located within theprofiled head 180 in order to affect rotation of the locking cap to afinal locked position.

While there have been illustrated and described particular embodimentsof the present invention, it will be appreciated that numerous changesand modifications will occur to those skilled in the art, and it isintended in the appended claims to cover all those changes andmodifications which fall within the true spirit and scope of the presentinvention.

1. A surgical instrument for shifting a spinal rod toward a couplingmember secured to a vertebra, the surgical instrument comprising: aclamp device for clamping onto the coupling member; a persuader armhaving an engagement portion for capturing the rod and being pivotalrelative to the clamp device for shifting the spinal rod toward theclamp device to position the rod above the coupling member; and a guideportion pivotal relative to the clamp device and operable to guide thepersuader arm for capturing of the rod by the engagement portion of thepersuader arm.
 2. The surgical instrument of claim 1, wherein the clampdevice and guide portion have a ratchet mechanism therebetweenconfigured to restrict pivoting of the persuader arm away from the clampdevice and permit ratcheted pivoting of the persuader arm toward theclamp device.
 3. The surgical instrument of claim 1, wherein the guideportion comprises a sleeve member through which the persuader arm islinearly shifted for positioning the engagement portion to capture therod.
 4. The surgical instrument of claim 3, wherein the persuader armhas exterior threads and wherein the persuader arm and the guide portionhave a drive mechanism therebetween to selectively engage the threads ofthe persuader arm so that the persuader arm may be controllably advancedand retracted toward and away when the drive mechanism is in an engagedposition and freely shifted through the guide portion when the drivemechanism is in a disengaged position.
 5. The surgical instrument ofclaim 1, wherein the engagement portion of the persuader arm comprises ahook at a distal end thereof.
 6. The surgical instrument of claim 1,wherein the distal end of the persuader arm has an axially extendingopening sized to permit at least a portion of the coupling member to fittherein.
 7. The surgical instrument of claim 1, wherein the instrumentfurther comprises an axial throughbore extending through the persuaderarm, and an elongate locking cap drive device sized to fit through thethroughbore to drive a locking cap into engagement with the couplingmember.
 8. The surgical instrument of claim 7, wherein the cap drivedevice has outer and inner shaft members, with the inner shaft memberdisposed within and coaxial with the outer shaft member, the inner andouter shaft members being configured to allow for independent rotationtherebetween.
 9. The surgical instrument of claim 8, wherein thepersuader arm and outer shaft member have a drive mechanismtherebetween, so that the outer shaft member is shifted linearlyrelative to the persuader arm upon rotation of the outer shaft.
 10. Thesurgical instrument of claim 8, wherein the inner shaft member has adrive end portion configured to engage a drive recess in the locking capso that rotation of the inner shaft member causes rotation of thelocking cap.
 11. A surgical instrument for maneuvering a spinal rodtoward a coupling member secured to a vertebra, the surgical instrumentcomprising: a clamp device for clamping the coupling member; a pivotalguide portion; a persuader arm having a distal end configured to engagea spinal rod, the persuader arm extending through the guide portion andaxially moveable therethrough; and a locking cap drive device fordriving a locking cap toward the spinal rod while the persuader arm isengaged with the spinal rod.
 12. The surgical instrument of claim 11,including a lock device for selectively engaging the persuader arm toprevent axial sliding of the persuader arm with respect to the guidedevice.
 13. The surgical instrument of claim 11, wherein the persuaderarm has a hook member at a distal end thereof.
 14. The surgicalinstrument of claim 11, wherein the distal end of the persuader arm hasa recess or opening configured to receive the coupling member so thatthe distal end of the persuader arm may surround the coupling memberwhile still engaged to the spinal rod.
 15. The surgical instrument ofclaim 11, wherein the guide portion and persuader arm include a ratchetmechanism therebetween for controlled, incremental pivoting of the guideportion and persuader arm.
 16. A method of shifting one or morevertebrae of a spine, the method comprising: anchoring a coupling memberto the vertebra; securing a rod to the spine so that the rod is adjacentto the coupling member; securing a clamp member to the coupling member;pivoting an engagement portion of a persuader arm to capture the rod;pivoting and axially shifting the persuader arm to maneuver the rodcaptured in the engagement end into the coupling member secured by theclamp member; and driving a locking cap through an axial channel in thepersuader arm in order to lock the rod to the coupling member.
 17. Themethod of claim 16, wherein the locking cap is driven by rotating athreaded drive member in the axial channel of the persuader arm.
 18. Themethod of claim 17, further comprising rotating the locking cap after ithas been driven into the coupling member.
 19. The method of claim 16,wherein pivoting of the persuader arm is accomplished with a rachetmechanism engaged so that pivoting of the engagement portion toward thecoupling member is allowed but pivoting away from the coupling member isnot allowed.
 20. The method of claim 16, further comprising shifting thepersuader arm axially without rotation to capture the rod.